Here is the introduction to the Wikipedia page on intersectionality:
Intersectionality is an analytic framework which attempts to identify how interlocking systems of power impact those who are most marginalized in society.[ Intersectionality considers that various forms of social stratification, such as class, race, sexual orientation, age, disability and gender, do not exist separately from each other but are interwoven together. While the theory began as an exploration of the oppression of women of color within society, today the analysis is potentially applied to all social categories (including social identities usually seen as dominant when considered independently).
So why might intersectionality matter? I can think of a few reasons:
1. Perhaps the signal extraction problem becomes more difficult in a non-linear fashion, when you are trying to peer through discrimination and identify underused talent for those with “multiple non-conformities.” You might have a good sense of what an undervalued black student will look like, but find it harder — indeed much harder — to identify an undervalued Surinamese Haitian trans female student in a wheelchair.
2. Multiple non-conformities are like tolls on a river. When there are multiple tolls, it doesn’t help commerce much to remove any one of them. Similarly, you might fix one dent in your car, but it may not be worthwhile to fix fifteen dents or indeed any one of them. No, I am not saying that individuals with multiple non-conformities are, in a quality sense, like dents in a car. Rather there is a common logic involving threshold effects. If you will come across as highly unusual in any case, perhaps you will not spend money to buy a nice suit. Or perhaps outside parties are more likely to help a person who has only one main “disability” or non-conformity to overcome, perceiving a much higher chance of success with the aid. Non-linear effects can discourage effort in a wide variety of cases.
3. Marginalized or minority communities may themselves exhibit prejudice against other non-conformities (for instance, some parts of the Jamaican community seem to be especially biased against gay individuals). That can make it harder for persons with multiple non-conformities to find allies.
4. Note that intersectionality may operate in a favor of a person rather than always operating against a person’s interests. For instance, black women arguably face less labor marker discrimination than do black men.
Overall, I believe the intersectionality concept is underrated by many people in the mainstream and on the political Right. It suffers from some of the problems that would be predicted by…the intersectionality concept.